The long term aim of this project is to determine the effect of conductive and sensorineural hearing losses on auditory perception in children and in adults. One major focus is the effect of chronic otitis media with effusion (OME) on the development of hearing in children. Specific aims in this area of the project include elucidating the causes of reduced MLDs in children with history of OME, and examining the relationship between stimulus complexity and monaural processing deficits in such children. An important related aim is to increase the understanding of the development of complex auditory perceptions related to auditory sound source segregation in normal-hearing children. The second major focus of the project is the effect of sensorineural hearing loss on the development of hearing in children. One specific aim here is to characterize early sensorineural hearing loss in terms of basic psychoacoustic abilities, and to compare results obtained with those of listeners with losses acquired in adulthood. A related aim will be to compare deprivation/acclimatization effects that are associated with hearing aids in children relatively large central neural commitment of cochlear regions that are normal but are adjacent to regions where hearing loss is severe. We will determine whether there is evidence for this in young listeners, using psychophysical and electrophysiological methods. A prevailing strategy across many of he proposed studies (both conductive and sensorineural) will be to compare results between adults and children when examining issues related to plasticity, in order to determine possible age effects. In both project areas, the primary psychophysical method will be three-alternative forced-choice testing with sound presentation over earphones. All phases of the project will include age-matched control subjects whose results will further our understanding of normal hearing. Data will be analyzed using analysis of variance and correlation procedures.